Coexistence primitives in power line communication networks

ABSTRACT

Systems and methods for setting a carrier-sensing mechanism in a PLC node are disclosed. In a PLC standard, coexistence is achieved by having the nodes detect a common preamble and backing off by a Coexistence InterFrame Space (cEIFS) time period to help the node to avoid interfering with the other technologies. In one embodiment, a PHY primitive is sent from the PHY to the MAC know that there has been a preamble detection. A two-level indication may be used - one indication after receiving the preamble and other indication after decoding the entire frame. The MAC sets the carrier-sensing mechanism based on the preamble detection.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of and claims benefit of U.S. patentapplication Ser. No. 13/923,097 filed Jun. 20, 2013, which claims thebenefit of the filing date of U.S. Provisional Patent Application No.61/662,176, which is titled “Primitives to Solve the NAV Updation forCoexistence Mechanisms” and was filed on Jun. 20, 2012, the disclosureof which is hereby incorporated by reference herein in its entirety.

BACKGROUND

Power line communications (PLC) include systems for communicating dataover the same medium that is also used to transmit electric power toresidences, buildings, and other premises, such as wires, power lines,or other conductors. In its simplest terms, PLC modulates communicationsignals over existing power lines. This enables devices to be networkedwithout introducing any new wires or cables. This capability isextremely attractive across a diverse range of applications that canleverage greater intelligence and efficiency through networking. PLCapplications include utility meters, home area networks, and applianceand lighting control.

PLC is a generic term for any technology that uses power lines as acommunications channel. Various PLC standardization efforts arecurrently in work around the world. The different standards focus ondifferent performance factors and issues relating to particularapplications and operating environments. Two of the most well-known PLCstandards are G3 and PRIME. G3 has been approved by the InternationalTelecommunication Union (ITU). IEEE is developing the IEEE P1901.2standard that is based on G3. Each PLC standard has its own uniquecharacteristics.

Using PLC to communicate with utility meters enables applications suchas Automated Meter Reading (AMR) and Automated Meter Infrastructure(AMI) communications without the need to install additional wires.Consumers may also use PLC to connect home electric meters to an energymonitoring device or in-home display monitor their energy consumptionand to leverage lower-cost electric pricing based on time-of-day demand.

As the home area network expands to include controlling home appliancesfor more efficient consumption of energy, OEMs may use PLC to link thesedevices and the home network. PLC may also support home and industrialautomation by integrating intelligence into a wide variety of lightingproducts to enable functionality such as remote control of lighting,automated activation and deactivation of lights, monitoring of usage toaccurately calculate energy costs, and connectivity to the grid.

The manner in which PLC systems are implemented depends upon localregulations, characteristics of local power grids, etc. The frequencyband available for PLC users depends upon the location of the system. InEurope, PLC bands are defined by the CENELEC (European Committee forElectrotechnical Standardization). The CENELEC-A band (3 kHz-95 kHz) isexclusively for energy providers. The CENELEC-B, C, D bands are open forend user applications, which may include PLC users. Typically, PLCsystems operate between 35-90 kHz in the CENELEC A band using 36 tonesspaced 1.5675 kHz apart. In the United States, the FCC has conductedemissions requirements that start at 535 kHz and therefore the PLCsystems have an FCC band defined from 154-487.5 kHz using 72 tonesspaced at 4.6875 kHz apart. In other parts of the world differentfrequency bands are used, such as the Association of Radio Industriesand Businesses (ARIB)-defined band in Japan, which operates at 10-450kHz, and the Electric Power Research Institute (EPRI)-defined bands inChina, which operates at 3-90 kHz.

Different PLC technologies may share the same PLC network and mayoperate in the same frequency range. Transmissions by nodes usingdifferent technologies may interfere with each other if the nodes do notrecognize when other technologies are using the channel. Apreamble-based coexistence mechanism can be used by different types ofPLC technologies to fairly share the medium. Coexistence provides theability for different narrow-band power line technologies to share thesame power line medium and to function simultaneously with an acceptablelevel of performance. For example, a preamble-based Carrier SenseMultiple Access (CSMA) can be used where different technologies haveoverlapping band plans.

SUMMARY OF THE INVENTION

Embodiments of the invention include systems and methods for setting aNetwork Allocation Vector (NAV) in a PLC node. In a PLC standard, suchas IEEE P1901.2/ITU, coexistence is achieved by having the nodes detecta common preamble and backing off by a Coexistence InterFrame Space(cEIFS) time period to help the node to avoid interfering with the othertechnologies. However, in existing systems, no mechanism has beendefined to allow a node to know when to set its NAV to perform the cEIFSback-off.

In one embodiment, an additional PHY primitive is added to let the MACknow that there has been a preamble detection. Traditionally, the PHYprovides an indication only after the complete reception of a frame. Atwo-level indication may be used—one indication after receiving thepreamble and other indication after decoding the entire frame.

A PD-PREAMBLE.Indication primitive is generated by the PHY afterreceiving the complete preamble. The primitive has the format:

PD-PREAMBLE-Indication { PT }wherein the value of PT (Preamble Type) is set to 0 if a node's nativepreamble is detected, and set to 1 if only a coexistence preamble isdetected (i.e., the node was unable to detect a foreign preamblegenerated by another technology node).

The receiver MAC responds to the new primitive as follows:

MAC sets its NAV to cEIFS on detecting a foreign preamble (i.e.,detecting only the coexistence preamble); and

MAC sets its NAV to EIFS on detecting a native preamble in addition tothe coexistence preamble.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, wherein:

FIG. 1 is a diagram of a PLC system according to some embodiments.

FIG. 2 is a block diagram of a PLC device or modem according to someembodiments.

FIG. 3 is a block diagram of a PLC gateway according to someembodiments.

FIG. 4 is a block diagram of a PLC data concentrator according to someembodiments.

FIG. 5 is a schematic block diagram illustrating one embodiment of asystem configured for point-to-point PLC.

FIG. 6 is a block diagram of an integrated circuit according to someembodiments.

FIG. 7 illustrates an example embodiment of a PLC network for a localutility PLC communications system.

FIG. 8 illustrates one embodiment of a system in which devices ofdifferent standards or protocols (e.g., technology A and technology B)may operate together in coexistence on a wire in a PLC network.

FIG. 9 illustrates one embodiment of a data packet that may becommunicated between the devices.

FIG. 10 is a block diagram illustrating a node sending a preambleindication primitive to a MAC layer from a PHY.

DETAILED DESCRIPTION

The invention now will be described more fully hereinafter withreference to the accompanying drawings. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein. Rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art. Oneskilled in the art may be able to use the various embodiments of theinvention.

FIG. 1 illustrates a power line communication network according to someembodiments. Medium voltage (MV) power lines 103 from subnode 101typically carry voltage in the tens of kilovolts range. Transformer 104steps the MV power down to low voltage (LV) power on LV lines 105,carrying voltage in the range of 100-240 VAC. Transformer 104 istypically designed to operate at very low frequencies in the range of50-60 Hz. Transformer 104 does not typically allow high frequencies,such as signals greater than 100 KHz, to pass between LV lines 105 andMV lines 103. LV lines 105 feed power to customers via meters or nodes106 a-n, which are typically mounted on the outside of residences 102a-n. Although referred to as “residences,” premises 102 a-n may includeany type of building, facility, electric vehicle charging node, or otherlocation where electric power is received and/or consumed. A breakerpanel, such as panel 107, provides an interface between meter 106 n andelectrical wires 108 within residence 102 n. Electrical wires 108deliver power to outlets 110, switches 111 and other electric deviceswithin residence 102 n.

The power line topology illustrated in FIG. 1 may be used to deliverhigh-speed communications to residences 102 a-n. In someimplementations, power line communications modems or gateways 112 a-nmay be coupled to LV power lines 105 at meter 106 a-n. PLCmodems/gateways 112 a-n may be used to transmit and receive data signalsover MV/LV lines 103/105. Such data signals may be used to supportmetering and power delivery applications (e.g., smart gridapplications), communication systems, high speed Internet, telephony,video conferencing, and video delivery, to name a few. By transportingtelecommunications and/or data signals over a power transmissionnetwork, there is no need to install new cabling to each subscriber 102a-n. Thus, by using existing electricity distribution systems to carrydata signals, significant cost savings are possible.

An illustrative method for transmitting data over power lines may use acarrier signal having a frequency different from that of the powersignal. The carrier signal may be modulated by the data, for example,using an OFDM technology or the like described, for example, G3-PLCstandard.

PLC modems or gateways 112 a-n at residences 102 a-n use the MV/LV powergrid to carry data signals to and from PLC data concentrator or router114 without requiring additional wiring. Data concentrator or router 114may be coupled to either MV line 103 or LV line 105. Modems or gateways112 a-n may support applications such as high-speed broadband Internetlinks, narrowband control applications, low bandwidth data collectionapplications, or the like. In a home environment, for example, modems orgateways 112 a-n may further enable home and building automation in heatand air conditioning, lighting, and security. Also, PLC modems orgateways 112 a-n may enable AC or DC charging of electric vehicles andother appliances. An example of an AC or DC charger is illustrated asPLC device 113. Outside the premises, power line communication networksmay provide street lighting control and remote power meter datacollection.

One or more PLC data concentrators or routers 114 may be coupled tocontrol center 130 (e.g., a utility company) via network 120. Network120 may include, for example, an IP-based network, the Internet, acellular network, a WiFi network, a WiMax network, or the like. As such,control center 130 may be configured to collect power consumption andother types of relevant information from gateway(s) 112 and/or device(s)113 through concentrator(s) 114. Additionally or alternatively, controlcenter 130 may be configured to implement smart grid policies and otherregulatory or commercial rules by communicating such rules to eachgateway(s) 112 and/or device(s) 113 through concentrator(s) 114.

FIG. 2 is a block diagram of PLC device 113 according to someembodiments. As illustrated, AC interface 201 may be coupled toelectrical wires 108 a and 108 b inside of premises 112 n in a mannerthat allows PLC device 113 to switch the connection between wires 108 aand 108 b off using a switching circuit or the like. In otherembodiments, however, AC interface 201 may be connected to a single wire108 (i.e., without breaking wire 108 into wires 108 a and 108 b) andwithout providing such switching capabilities. In operation, ACinterface 201 may allow PLC engine 202 to receive and transmit PLCsignals over wires 108 a-b. In some cases, PLC device 113 may be a PLCmodem. Additionally or alternatively, PLC device 113 may be a part of asmart grid device (e.g., an AC or DC charger, a meter, etc.), anappliance, or a control module for other electrical elements locatedinside or outside of premises 112 n (e.g., street lighting, etc.).

PLC engine 202 may be configured to transmit and/or receive PLC signalsover wires 108 a and/or 108 b via AC interface 201 using a particularfrequency band. In some embodiments, PLC engine 202 may be configured totransmit OFDM signals, although other types of modulation schemes may beused. As such, PLC engine 202 may include or otherwise be configured tocommunicate with metrology or monitoring circuits (not shown) that arein turn configured to measure power consumption characteristics ofcertain devices or appliances via wires 108, 108 a, and/or 108 b. PLCengine 202 may receive such power consumption information, encode it asone or more PLC signals, and transmit it over wires 108, 108 a, and/or108 b to higher-level PLC devices (e.g., PLC gateways 112 n, dataaggregators 114, etc.) for further processing. Conversely, PLC engine202 may receive instructions and/or other information from suchhigher-level PLC devices encoded in PLC signals, for example, to allowPLC engine 202 to select a particular frequency band in which tooperate.

FIG. 3 is a block diagram of PLC gateway 112 according to someembodiments. As illustrated in this example, gateway engine 301 iscoupled to meter interface 302, local communication interface 304, andfrequency band usage database 304. Meter interface 302 is coupled tometer 106, and local communication interface 304 is coupled to one ormore of a variety of PLC devices such as, for example, PLC device 113.Local communication interface 304 may provide a variety of communicationprotocols such as, for example, ZigBee, Bluetooth, Wi-Fi, Wi-Max,Ethernet, etc., which may enable gateway 112 to communicate with a widevariety of different devices and appliances. In operation, gatewayengine 301 may be configured to collect communications from PLC device113 and/or other devices, as well as meter 106, and serve as aninterface between these various devices and PLC data concentrator 114.Gateway engine 301 may also be configured to allocate frequency bands tospecific devices and/or to provide information to such devices thatenable them to self-assign their own operating frequencies.

In some embodiments, PLC gateway 112 may be disposed within or nearpremises 102 n and serve as a gateway to all PLC communications toand/or from premises 102 n. In other embodiments, however, PLC gateway112 may be absent and PLC devices 113 (as well as meter 106 n and/orother appliances) may communicate directly with PLC data concentrator114. When PLC gateway 112 is present, it may include database 304 withrecords of frequency bands currently used, for example, by various PLCdevices 113 within premises 102 n. An example of such a record mayinclude, for instance, device identification information (e.g., serialnumber, device ID, etc.), application profile, device class, and/orcurrently allocated frequency band. As such, gateway engine 301 may usedatabase 305 in assigning, allocating, or otherwise managing frequencybands assigned to its various PLC devices.

FIG. 4 is a block diagram of PLC data concentrator or router 114according to some embodiments. Gateway interface 401 is coupled to dataconcentrator engine 402 and may be configured to communicate with one ormore PLC gateways 112 a-n. Network interface 403 is also coupled to dataconcentrator engine 402 and may be configured to communicate withnetwork 120. In operation, data concentrator engine 402 may be used tocollect information and data from multiple gateways 112 a-n beforeforwarding the data to control center 130. In cases where PLC gateways112 a-n are absent, gateway interface 401 may be replaced with a meterand/or device interface (now shown) configured to communicate directlywith meters 116 a-n, PLC devices 113, and/or other appliances. Further,if PLC gateways 112 a-n are absent, frequency usage database 404 may beconfigured to store records similar to those described above withrespect to database 304.

FIG. 5 is a schematic block diagram illustrating one embodiment of asystem 500 configured for point-to-point PLC. The system 500 may includea PLC transmitter 501 and a PLC receiver 502. For example, a PLC gateway112 may be configured as the PLC transmitter 501 and a PLC device 113may be configured as the PLC receiver 502. Alternatively, the PLC device113 may be configured as the PLC transmitter 501 and the PLC gateway 112may be configured as the PLC receiver 502. In still a furtherembodiment, the data concentrator 114 may be configured as either thePLC transmitter 501 or the PLC receiver 502 and configured incombination with a PLC gateway 112 or a PLC device 113 in apoint-to-point system 500. In still a further embodiment, a plurality ofPLC devices 113 may be configured to communicate directly in apoint-to-point PLC system 500 as described in FIG. 5. Additionally, thesubnode 101 may be configured in a point-to-point system 500 asdescribed above. On of ordinary skill in the art will recognize avariety of suitable configurations for the point-to-point PLC system 500described in FIG. 5.

FIG. 6 is a block diagram of a circuit for implementing the transmissionof multiple beacon frames using different modulation techniques on eachtone mask in a PLC network according to some embodiments. In some cases,one or more of the devices and/or apparatuses shown in FIGS. 1-5 may beimplemented as shown in FIG. 6. In some embodiments, processor 602 maybe a digital signal processor (DSP), an application specific integratedcircuit (ASIC), a system-on-chip (SoC) circuit, a field-programmablegate array (FPGA), a microprocessor, a microcontroller, or the like.Processor 602 is coupled to one or more peripherals 604 and externalmemory 603. In some cases, external memory 603 may be used to storeand/or maintain databases 304 and/or 404 shown in FIGS. 3 and 4.Further, processor 602 may include a driver for communicating signals toexternal memory 603 and another driver for communicating signals toperipherals 604. Power supply 601 provides supply voltages to processor602 as well as one or more supply voltages to memory 603 and/orperipherals 604. In some embodiments, more than one instance ofprocessor 602 may be included (and more than one external memory 603 maybe included as well).

Peripherals 604 may include any desired circuitry, depending on the typeof PLC system. For example, in an embodiment, peripherals 604 mayimplement local communication interface 303 and include devices forvarious types of wireless communication, such as Wi-Fi, ZigBee,Bluetooth, cellular, global positioning system, etc. Peripherals 604 mayalso include additional storage, including RAM storage, solid-statestorage, or disk storage. In some cases, peripherals 604 may includeuser interface devices such as a display screen, including touch displayscreens or multi-touch display screens, keyboard or other input devices,microphones, speakers, etc.

External memory 603 may include any type of memory. For example,external memory 603 may include SRAM, nonvolatile RAM (NVRAM, such as“flash” memory), and/or dynamic RAM (DRAM) such as synchronous DRAM(SDRAM), double data rate (DDR, DDR2, DDR3, etc.) SDRAM, DRAM, etc.External memory 603 may include one or more memory modules to which thememory devices are mounted, such as single inline memory modules(SIMMs), dual inline memory modules (DIMMs), etc.

FIG. 7 illustrates an example embodiment of a PLC network 700 for alocal utility PLC communications system. Network 700 includes LV nodes702 a-n and each of the nodes 702 a-n is connected to MV power line 720through a corresponding transformer 710 a-n and LV line 706 a-n. Router,or modem, 714 is also connected to MV power line 720. A sub-network 728,or neighborhood 728, may be represented by the combination of nodes 702a-n and router 714. Master router 712 and router 716 are also connectedto MV line 720, which is powered by power grid 722. Power grid 722represents the high voltage power distribution system.

Master router 712 may be the gateway to telecommunications backbone 724and local utility, or control center, 726. Master router 712 maytransmit data collected by the routers to the local utility 726 and mayalso broadcast commands from local utility 726 to the rest of thenetwork. The commands from local utility 726 may require data collectionat prescribed times, changes to communication protocols, and othersoftware or communication updates.

During UL communications, the nodes 702 a-n in neighborhood 728 maytransmit usage and load information (“data”) through their respectivetransformer 710 a-n to the MV router 714. In turn, router 714 forwardsthis data to master router 712, which sends the data to the utilitycompany 726 over the telecommunications backbone 724. During DLcommunications (router 714 to nodes 702 a-n) requests for data uploadingor commands to perform other tasks are transmitted.

In accordance with various embodiments, nodes 702 a-n employ a CarrierSense Multiple Access with Collision Avoidance (CSMA/CA) mechanism thatcombines energy detection and preamble detection to access the PLCnetwork. The nodes may do either of the following CSMA/CA methods toaccess the channel: (1) run energy detection first and then use preambledetection only after energy detection returns positive, or (2) run bothenergy detection and preamble detection simultaneously. The CSMA-CAalgorithm is used before the transmission of data or MAC command frames.

FIG. 8 illustrates one embodiment of a system in which devices ofdifferent standards or protocols (e.g., technology A and technology B)may operate together in coexistence on a wire 801 in a PLC network. Inthis example, the system may include PCL devices 802, 803 that usetechnology A to communicate. In addition, the system may include anotherPLC 804 that uses technology B to communicate with other nodes (notshown). For example, devices 802, 803 may use an IEEE P1901.2technology, and device 804 may use an ITU-G3 technology. Devices usingdifferent technologies may coexist in the same PLC system using acoexistence preamble.

FIG. 9 illustrates one embodiment of a data packet 901 that may becommunicated between the devices 802 and 803 of FIG. 8. In oneembedment, the data packet 901 may include a coexistence preamble 902, atechnology-specific preamble 903, a frame control header (FCH) 904, anda data payload 905. When a device listens to the PLC medium to accessthe channel for communication, it may detect preambles 902, 903 on thechannel. Coexistence preamble 902 comprises a sequence of symbols thatare agreed upon across different technologies (i.e., it will be detectedby both technologies A and B). Technology-specific preamble 903 isassociated with a particular technology (i.e., it will be detected byonly one of technology A or B).

When a device listens on the PLC channel, it will attempt to decode anyreceived data. For example, when data packet 901 is received, thereceiving device (e.g., node 802) will detect coexistence preamble 902.If packet 901 was sent by a transmitter using the same technology (e.g.,node 803), then the receiving device will also detect thetechnology-specific preamble 903 as a “native” preamble. The receivingdevice will further detect and decode the information in FCH 904 and905. On the other hand, if packet 901 was sent by a transmitter using adifferent technology (e.g., node 804), then the receiving device willnot detect the technology-specific preamble 903 because it is a“foreign” preamble. In this case, the foreign preamble 903—along withFCH 904 and data payload 905—would appear to the receiving device asnoise and would not be detected.

When one technology is used on the PLC network, the nodes may use anExtended InterFrame Space (EIFS) that is specifically defined for thattechnology. In PLC networks where there are devices with differenttechnologies, a common back-off time for all devices in the networkreferred to as coexistence Extended InterFrame Space (cEIFS) may bedefined. A device will back-off for cEIFS if it detects a coexistencepreamble 902 on the channel. This enables fair channel access fordifferent technologies in a coexistence system regardless of the numberof devices exist on the system for each technology.

In one embodiment, a coexistence preamble sequence may consist ofMrepeated symbols, such as repeated SyncP format symbols. Alternatively,a new SyncC symbol may be defined specifically for coexistence. Thevalue M may be chosen such that the coexistence sequence 902 is as largeas the maximum packet size supported by all the technologies competingfor channel access present in the network. In some embodiments the SyncPor SyncC symbol may be defined as an OFDM symbol with selectedsubcarriers modulated with phase values between (0-2π). In otherembodiments, the SyncP or SyncC symbols may consist of chirp sequences,pseudo-random bit sequences, barker sequences, or an arbitrary +/−1sequence.

When a device detects a coexistence preamble on the channel, it willback-off the channel to allow the transmitting node to complete thetransmission. The duration of the back-off interval is set in a NetworkAllocation Vector (NAV). As a condition to accessing the medium, the MAClayer on a node checks the value of NAV, which is a counter thatrepresents the amount of time before an attempt can be made to send aframe. The NAV must be zero before a node can attempt to send a frame.

Coexistence is achieved by having the nodes detect a common preamble andbacking off by a cEIFS (Coexistence EIFS time period) to help avoid itinterfering with the other technologies. However, no mechanism has beendefined to allow a node to know when to set its NAV to perform the same.

FIG. 10 is a block diagram illustrating a node 1001 having a MAC layer1002 and a PHY 1003. MAC 1002 is a sublayer of a data link layer thatformats data to be communicated over the associated PHY layer. PHY 1003provides an interface between the MAC sublayer and the physical mediumor power line. MAC 1002 includes NAV 1004, which is used to manage theback-off duration between attempts to access the channel.

In one embodiment, a PHY primitive—PD-Preamble-Indication 1005—is usedto let MAC 1002 know when PHY 1003 has detected a preamble on thechannel. PD-Preamble-Indication 1005 may be a two-level indication thatprovides one indication after receiving the preamble and anotherindication after decoding the entire frame.

The PD-Preamble-Indication 1005 may be generated by PHY 1003 afterreceiving the complete preamble and may be in the following format:

PD-Preamble-Indication { Preamble Type (PT) }wherein PT is set to 0 when a native preamble is detected, and is set to1 when a non-native (or alien or foreign) preamble is detected.

Upon receiving the PD-Preamble-Indication 1005, the MAC 1002 operates asfollows:

set NAV 1004 to cEIF S if a non-native preamble is detected (i.e.,PT=1); and

set NAV 1004 to EIFS if a native preamble is detected (i.e., PT=0).

A native preamble will be detected, if present, by the PHY afterdetecting the coexistence preamble. The presence of a non-nativepreamble may be detected by the PHY by the absence of a native preamblefollowing a coexistence preamble. The non-native preamble will look likenoise to the PHY because it is not defined for the technology used bythe PHY.

Many modifications and other embodiments of the invention(s) will cometo mind to one skilled in the art to which the invention(s) pertainhaving the benefit of the teachings presented in the foregoingdescriptions, and the associated drawings. Therefore, it is to beunderstood that the invention(s) are not to be limited to the specificembodiments disclosed. Although specific terms are employed herein, theyare used in a generic and descriptive sense only and not for purposes oflimitation.

What is claimed is: 1-13. (canceled)
 14. A method, comprising:performing by a power line communication (PLC) device, detecting acoexistence preamble on a PLC channel; configuring a preamble indicationprimitive in a first format if a native preamble is detected in additionto the coexistence preamble; configuring the preamble indicationprimitive in a second format if a native preamble is not detected inaddition to the coexistence preamble; setting a carrier-sensingmechanism based upon the preamble indication primitive; and sending thepreamble indication primitive from a PHY layer to a MAC layer on the PLCdevice.
 15. The method of claim 14, further comprising: setting thecarrier-sensing mechanism to a first interframe spacing value, if anative preamble is detected in addition to the coexistence preamble; andsetting the carrier-sensing mechanism to a second inteframe spacingvalue, if a native preamble is not detected in addition to thecoexistence preamble.
 16. The method of claim 14, further comprising:setting the carrier-sensing mechanism to a native extended interframespacing (EIFS) value, if a native preamble is detected in addition tothe coexistence preamble; and setting the carrier-sensing mechanism to acoexistence extended interframe spacing (cEIFS), if a native preamble isnot detected in addition to the coexistence preamble.
 17. A device,comprising: a receiver configured to monitor a power line communication(PLC) channel of the PLC network, the receiver further configured toperform a preamble detection operation on the PLC channel; a mediumaccess control (MAC) layer adapted to receive the preamble indicationprimitive from the PHY layer a carrier-sensing mechanism adapted to beset by the MAC based upon the preamble indication primitive; and aphysical (PHY) layer adapted to configure a preamble indicationprimitive, the preamble indication primitive configured in a firstformat if a native preamble is detected by the receiver in addition tothe coexistence preamble, and the preamble indication primitiveconfigured in a second format if a native preamble is not detected inaddition to the coexistence preamble.
 18. The device of claim 17,wherein the carrier-sensing mechanism is set to a first interframespacing value, if a native preamble is detected in addition to thecoexistence preamble; and the carrier-sensing mechanism is set to asecond inteframe spacing value, if a native preamble is not detected inaddition to the coexistence preamble.
 19. The device of claim 17,wherein the carrier-sensing mechanism is set to a native extendedinterframe spacing (EIFS) value, if a native preamble is detected inaddition to the coexistence preamble, and the carrier-sensing mechanismis set to a coexistence extended interframe spacing (cEIFS), if a nativepreamble is not detected in addition to the coexistence preamble.
 20. Amethod, comprising: performing by a power line communication (PLC)device, determining whether a native preamble or a non-native preambleis detected after a coexistence preamble on a PLC channel; configuring apreamble indication primitive in a first format if a native preamble isdetected in addition to the coexistence preamble; configuring thepreamble indication primitive in a second format if a non-nativepreamble is detected in addition to the coexistence preamble; setting acarrier-sensing mechanism based upon the preamble indication primitive;and sending the preamble indication primitive from a PHY layer to a MAClayer on the PLC device.
 21. The method of claim 20, further comprising:setting the carrier-sensing mechanism to a first interframe spacingvalue, if a native preamble is detected in addition to the coexistencepreamble; and setting the carrier-sensing mechanism to a secondinteframe spacing value, if a non-native preamble is detected inaddition to the coexistence preamble.
 22. The method of claim 20,further comprising: setting the carrier-sensing mechanism to a nativeextended interframe spacing (EIFS) value, if a native preamble isdetected in addition to the coexistence preamble; and setting thecarrier-sensing mechanism to a coexistence extended interframe spacing(cEIFS), if a non-native preamble is detected in addition to thecoexistence preamble.